The PET and Mass Spectrometry (MS) Core provides the Center with the capability to study critical phenomena at the tissue, cellular, and genetic levels in both humans and living animals; non-invasively with PET. The core allows complex studies to be performed by the Human Subjects and Animal Research Cores at the MGH and SHC and provides investigators with the capability to apply PET and MS technology to test scientific hypotheses without the need to become experts in the technologies themselves. Conventional PET cameras and pPET devices provide the ability to study animals more than once, allows each animal to serve as its own control, and allows interventional strategies to be followed over time. Furthermore, identical studies can also be conducted non-invasively directly in normal human volunteers and patients. The DPET is mobile and makes imaging skeletal muscle possible in acutely ill intensive care patients. Further development of molecular imaging methodologies will enable imaging of fatty acid metabolism, mitochondrial function, gene expression and apoptosis; initially in mice and ultimately in humans. Services offered by the PET component of the core, include: (1) Design and development of new imaging agents. (2) Routine production of existing PET agents. (3) Routine execution of existing imaging protocols and data analyses. (4) Development of new instrumentation. The MS component of the core supports research that allows our investigators to apply stable isotope tracers for studying: amino acid, glucose and lipid metabolism, nitrate/nitric oxide, protein turnover, proteomics and substrate kinetics/oxidation. Services to the center, include: (1) Timely and accurate determinations of isotope enrichments of tracers and their derivatives in biological samples. (2) Development of new methods for isotope analyses of compounds in blood, tissues, and urine to meet the needs of our investigators. (3) Quality control for all analysis conducted in support of studies that use stable isotopes. This facility enables research in all 4 projects and funds to support these activities directly are included in each project.